Modelling Bird Songs: Voice Onset, Overtones and Registers

We analyze two symmetric two-mass models of the avian syrinx. Our first model applies to songbirds and is a rescaled version of the well-known human two-mass model. Our second model (trapezoidal model) introduces a smoother geometry and is used to simulate the ring dove (Streptopelia risoria) syrinx. Simulations show that both models exhibit self-sustained vibrations. We show that the occurrence of collisions and the intensity of harmonics depend strongly on the configuration of the syrinx. The songbird model does not present instabilities. The trapezoidal model, however, displays coexisting limit-cycles that represent vibrations with, and without collisions at the same pressure. Register-like transitions are accompanied by subharmonics and deterministic chaos.